Kaguya

Kaguya is a beautiful girl that Amaterasu first meets when she is exploring The Emperor's Palace in Sei'an City. They hear a young lady crying only to find out it is Kaguya sobbing in her jail cell. She was imprisoned, for no reason, by The Emperor who is possessed by Blight. She informs them that she is Mr. Bamboo's granddaughter.

If Amaterasu and Issun travel to the bamboo forest at the back of Sasa Sanctuary the find out the real truth about Kaguya. She is not Mr. Bamboo's granddaughter but instead he was found her as a baby one day in a large metal bamboo shoot and he and his late wife raised Kaguya as their own child.
When Kaguya is released from prison she will travel back to Sasa Sanctuary where Amaterasu can help her in a Digging mini game. This mini game unearths a giant metal rocket which Kaguya sadly uses to return to space to look for her real home.

We can piece together that Kaguya was not human but instead a member of the Moon Tribe. She was placed on the rocket as a baby to save her from the terrible disaster that was happening to them, the same disaster that caused Waka to flee. The rocket that she travelled with used very advanced technology the kind that only the Moon Tribe could build, the rocket was also marked with the Moon Tribe's Crest.
According to Mr Bamboo, Kaguya would cry at the sight of the full moon showing her attachment too it. Her hair decorations also resemble rabbit ears showing another connection to the moon as Japanese legends believe the face on the moon is that of a rabbit.

Finally Kaguya's story is based on the Japanese legend of "The Tale of the Bamboo Cutter". In this story the main character "Kaguya-Hime" was from Tsuki-no Miyako ("The Capital of The Moon"). Kaguya-Hime was a lot like Okami's Kaguya she had hair that shined like gold and was strongly drawn to the moon. Some versions of the story said that Kaguya-Hime was sent to earth to save her from a celestial war.
These similarities make it certain that Kaguya was a member of the Moon Tribe who was sent to earth to save their race.